In RHEL 3, the serious, professional, expensive release; the open(2) man page contains the following text:

BUGS
"The thing that has always disturbed me about O_DIRECT is that the
whole interface is just stupid, and was probably designed by a deranged
monkey on some serious mind-controlling substances." -- Linus

This text doesn't appear in the version of the open(2) man page in Redhat 9 (which RHEL 3 was largely based on).